For attaching a printed poster, an advertisement or the like to an object to be attached, such as wall face, glass face, pillar, board, locker, bookshelf or the like, heretofore an adhesive agent, an adhesive tape or the like has been used. However, in case where a poster, an advertisement or the like is attached to an object to be attached with an adhesive agent or an adhesive tape, it is difficult to readily peel away after use, and there are some problems in that the paste may remain after peeling from the surface of the object to be attached or the coating on the surface of the object to be attached may peel away, therefore resulting in that the object may gradually get dirty or its original surface smoothness may be lost.
As a method of posting a poster, an advertisement or the like not using an adhesive agent or an adhesive tape, there is proposed an adsorption-type film that enables attaching by an electrostatic force. For example, Patent References 1 and 2 propose an electrostatic adsorbability-given polyvinyl chloride film; and Patent Reference 3 proposes an electrostatic adsorbability-given polypropylene film.
However, though a specific substance is incorporated in these films for keeping the electrostatic adsorbability, the films still have a problem in that their durability of the adsorbability is insufficient. In addition, as lacking in printability/recordability, these films have another problem in that, when they are used as posters or the like, a desired article must be attached thereto and then the films are used as an embodiment of posters or the like.
Patent References 4 to 6 propose a porous film of an electrostatically-adsorbable polymer. By making the film a porous film, the chargeable surface area becomes large, the ability to hold electrified charges is enhanced and the durability of the adsorbability is enhanced. However, the porous film is formed according to a coating method, and therefore the polymer usable for it is limited to a polymer soluble in a solvent. In addition, since the polymer has high moisture permeability and since the pores formed therein are not closed pores (but are interconnected), the film has defects in that the charge-retaining ability thereof varies depending on the external humidity and the electrostatic adsorbability thereof is influenced by humidity.
Patent Reference 7 proposes a film of a dielectric material that contains flat-shaped pores and has a high unipolar charge given to the inside thereof. The film produced according to the method has an advantage of high and long-lasting electrostatic adsorbability; however, when this is printed and is used as a poster or a label, there occur problems in that, in printing thereon, the runnability of the film on a printing machine is extremely bad because of its own electrostatic adsorbability and the film may stick to rolls and others thereby causing pattern misalignment or may catch dust and contaminants during printing and may thereby get dirty. To solve the problems, the formed film must be once printed, and then again given a unipolar charge; however, the process is complicated and is extremely inconvenient for use of the film as printing paper to be printed with various patterns. As such, originally, the film of Patent Reference 7 is not taken into consideration for printing, and is therefore defective in that the ink adhesiveness to it is insufficient.